AHC line / Pipe replacement Procedure

[CrackedManifold]

Sorry if this has been asked already, didn’t find much via search.

Recently purchased an ‘05 LX at a good price. I was infatuated at how clean the frame, body, and interior was (for the northeast), that I missed inspecting the whole AHC system. The hydraulic lines are pretty crusty/rusty at all 4 corners. Despite that, they’re not leaking…. Yet…

Does anyone have a reliable source for AHC lines? Only available units seem to be overseas.

If not, I’ve been considering the OEM LC suspension swap. Local Junk yards have donor trucks I can pull the TBs and coils from. I would be doing the work myself.

Not sure of the overall health of the AHC as the truck is stuck in N mode. I haven’t plugged the Techstream software in yet. But considering the rusty components, it may justify the suspension swap.

 

[CrackedManifold]

Little Update:

So performed the AHC reset via shorting the Tc & E1 and lo-and-behold, the system now works. Cycles through all the heights as well. Also did the graduation test and it looks like it’s showing around 12-14 gradations. Hard to tell since it looks like the reservoir is a little overfilled (level is at the reservoir “seam”), but the globes look in good shape and the ride quality is nice. With that being said, it would be a true shame to rip out this system.

Despite the lines being buried between the body and frame, the repair/replacement looks very doable.

If I can find a reliable source for new lines, I’ll be the Guinea pig and make a DIY replacement tutorial. These cruisers aren’t getting any younger so a how-to is long over due. Overseas vendors show to stock them such as the fleabay and Partsouq? But skeptical. I’ll even consider a rust-free used set if anyone has some laying around.

Any reliable source for the suspension fluid as well?

 

[OGBeno]

The lines are all available from your Toyota dealer as is the fluid.

 

[CrackedManifold]

The lines are all available from your Toyota dealer as is the fluid.

Well I'll be darned; my local dealership said they're no longer available (Toyota dealership). I may take my chances with one of these overseas vendors as I can get a full rear set for the price of one versus dealership prices. Thanks for that info.

 

[CrackedManifold]

Was able to source the hydraulic lines and other misc parts from a donor vehicle. As much as I wanted to buy new, the tariffs and shipping fee horror stories lead me to source used domestically instead. The (st)ealership wanted to charge me $275 in shipping fees per line alone.

New O-rings and gaskets are on order. Still have to source AHC fluid.

I'll be replacing one line per side over the next period, starting with the passenger rear and drivers front. It seems that the general consensus is these are the common failure corners.

For the driver's rear, it looks like there is no choice but to drop the gas tank for this job. I'll replace gas tank straps while I have the tank out. Driver's side front, the transmission crossmember will probably have to be removed. I've begun soaking all associated bolts with PB blaster (Northeast truck).

Besides that, the replacement seems pretty straight forward. The challenging part looks to be working at the top bolts. I'd like to avoid cutting holes in the floor but will if needed.

I'll keep this thread updated as I complete the replacement.

 

[CrackedManifold]

Just finished replacing the passenger rear line. Was able to complete the job by working in the wheel well and underside rear. I did not have to cut a hole in the floor, or take out the exhaust etc.

As promised, here is somewhat of a DIY procedure;

Tools used:

Jack & jack stands
Flashlight
12mm flex head ratcheting wrench (long)
1/4in and 3/8 pivot head ratchet
12mm socket
10mm offset wrench
17mm line wrench
Various pry bars and long flat head
Needlenose pliers

With this being a NE truck, I begun by marinating all the bolts with PB blaster a few weeks before the repair.

1) Remove the spare tire
2) Set the AHC height to Low
3) Remove the rear passenger tire and secure with jackstands.

4) Bleed the accumulator. Be sure to not be under the vehicle while doing this. I used a 10mm offset wrench. Open very slowly. Also connected a hose to the bleed nipple to catch the fluid in the bottle. Once the flow stops, close the bleeder screw.

4.5) Unbolt the hydraulic line from the accumulator using a 17mm line wrench. I’m my case, the fitting was seized in the accumulator. I cut the line with a hacksaw and threw a socket on it instead.

5) Bracket holding the pipe is bolted on top of the frame on the right side of the wheel well, reaching from under the frame, over the muffler. There is a wire harness connected to it that will have to be removed along with a 12mm bolt. You can access both by working inside the wheel wheel. I used a 1/4 flex head ratchet to break free the bolt, then the 12mm flex head ratcheting wrench to finish. There is not much clearance for the ratchet to remove the bolt.

6) Using the 12mm flex head ratcheting wrench, I unbolted the shock side bracket by accessing each 12mm nut from the wheel wheel between the body seam and frame (move the wiring harness out of the way) and backside rear.

Once the bracket was unbolted from the upper shock, I used a pry bar to pop off the line.

8). At this point, You should be able to snake the line out. Sitting in the wheel well, working from below the frame, I was able to remove the line from working it out above the muffler. There is a wiring harness clipped to the line and frame. Move those out of the way and work the actuator side of the line out, then the shock side.

 

[CrackedManifold]

9). Since I’m using a used line, I replaced the o-ring and spacer with new OEM.

10). Working from the wheel well, slide the actuator side of the line in above the muffler and work the shock side of the line along the frame rail to the shock (don’t forget to install the spacer on the shock stud). Line up the line to the mounting bracket above the frame and slide the other end of the line over the frame rail, below the wiring harness. Bolt everything back up to where they belong. I used anti-seize on the shock top and frame rail bolts for future removal.

11). Open up the bleeder screw and Jack the axle hub up. This will force suspension fluid from the shock through the new hydraulic line and ensure there is no air in this part of the system. Jack up until a steady stream of fluid flows out. Close the bleeder screw, then lower the Jack.

12). Finally, put everything back together and clean up.

13). Perform the appropriate bleed sequence for the AHC system. I did not do this, thinking there is no air present in the system. However, it sounds like there is air trapped in the control valve assembly and getting an OFF light when trying to raise to High. I’ll perform the bleed sequence tomorrow. EDIT: turns out the reservoir fluid was empty. Topped off the reservoir, performed the ECU reset and ran multiple height cycles to work out the air bubbles.

Overall, this was not a bad repair to do. Did not have to drop the muffler, cut a hole in the floor etc. repair took me about 3-3.5hrs to complete. Despite taking care of my 5-month old baby in between.
Anyway, Hope this helps fellow AHC owners experiencing this dilemma.

 

[mrkdwrds]

Nice writeup!

If you have not seen it, I'd recommend looking into the sales that the Southeast US dealers run, which comes out to 25% below their already discounted prices. MUCH cheaper than my local dealer so I mostly get parts from them. Serra of Decatur is a favorite here and I've had good luck with them, even with large/awkward items like LCAs. Free shipping, no tax out of state, and great deals. Their current sale runs for another 2 days. More here: Toyota sale, 25% off wholesale and free shipping WOW - https://forum.ih8mud.com/threads/toyota-sale-25-off-wholesale-and-free-shipping-wow.1320195/page-41

Also, Partsouq is great for parts diagrams. Punch your VIN in and you can find details for parts, then plug those into Serra to order. Partsouq used to be a great deal pre-tariff but seems easier these days to order from a domestic dealer.

 

[CrackedManifold]

The drivers side rear looks like it will be the same procedure, with the exception of dropping the driveshaft and fuel tank. I’ll be replacing that side soon and will update this thread.

the few threads I’ve read, it seems that the driver and passenger front lines are an absolute bear to replace because of their length. Read some post of others having to remove the transmission crossmember to removing the exhaust manifolds. ‘Eff that. I’m thinking about cutting the front lines in half and installing hydraulic compression or flare fittings to make the install easier. Once again, I’ll update this thread.

 

[suprarx7nut]

nice work. Cool to see someone figuring that out.

 

[CrackedManifold]

Just finished replacing the Driver side rear hydraulic line. I was able to complete the repair without having to drop the fuel tank or cut a hole in the floor.

The drivers side pretty much mirrors the passenger side in terms of installation so the same procedure for the passenger rear removal can be used here;

Obviously the fuel tank is in the way with this one so the line will have to be intricately snaked out and in between the inner frame rail and side of the fuel tank. This is where petite hands and long arms shine; if you have sausage fingers and T-Rex arms this side might be a little more tedious. Accessing the line bracket bolt and wiring harness in the wheel well is more of a “feel for” than visual:

Once the line is unbolted, pull the shock side line out from between the back of the fuel tank and control arm crossmember.

There are a few wiring harnesses running along the top of the frame, above the accumulator which will have to be disconnected in order to snake the line forward. I opted to just cut the tape as I could not get a good enough grip to disconnect off the frame.

 

[CrackedManifold]

Once the wiring harnesses is disconnected, slide the hydraulic line forward, towards the front of the vehicle, to the front fuel tank strap. There will be enough clearance here to slide the accumulator side line out. This will take some “finessing” to get the line out.

To install, snake the accumulator fitting side of the line above the frame rail, right behind the front fuel tank strap. Reach over the other side of the frame rail and fish the line through:

 

[CrackedManifold]

Once the accumulator side line is fished thru above the frame, slide the line back towards the accumulator. Thread the union fitting to the accumulator (don’t tighten yet) as it’s easier to line up as-is.

Horseshoe the soft end of the line and feed the shock end through between the back of the fuel tank and rear crossmember. Id suggest using a clothes hanger at the end of the fitting to help pull the line to the shock.

Pop the hard line back in between the inner frame rail and fuel tank. It will take a little finessing to get where it needs to seat.

Bolt everything back up, bleed & fill, call it a day. This side took me about 3hrs to complete, despite the tank being in the way. But again, I did not have to drop the tank for the replacement.

I’ll say though, this job would be a 100 times easier with the tank removed. If you have to replace your fuel tank, consider swapping out the drivers side AHC line out as well. Chances if the tank is rotted, this line may be rotted too.

 

[CrackedManifold]

Got around to replacing the driver’s front AHC line and boy, what a bear of a job that was.

Despite all the bolts being easily accessible and AHC line in plain view, there are a lot of obstacles in the way and the length of the line adds to the difficulty. I had to somewhat “bubba” (bend & pry) the line out and in place. Unless you want to remove the catalytic converter and/or tranny crossmember, steering shaft, this is really the only alternative option.

Unfortunately I don’t have many photos on this how-to as most of my time was spent in trial & error removing and installing the AHC line but will try to be as detailed as possible;

Tools used: 3/8 12mm socket and ratchet, 12mm long pivot head ratcheting wrench, 1/2 17mm socket and ratchet, 10mm and 17mm line wrench, pry bar, hacksaw, piece of wood, Jack and Jack stands.


1). Lower the vehicle height to “N” mode.
2) Remove the wheel and support on jackstands.
3) Remove (or move aside) inner wheel well splash guard.

4) Bleed the accumulator.

5) Unbolt the AHC line from the accumulator, frame bracket, and shock mount (in my case, the union fitting to accumulator was seized, so I had to cut the line to fit a socket on).

6) Now that the line is free, you’ll notice that the front exhaust pipe and transmission crossmember are in the way for a straightforward removal. I found the best approach for removal and install is to slide it out towards the rear of the vehicle and install in the same fashion. Slight bending and reshaping of the line will occur. Begin by unplugging the wiring harness from the AHC height control valve.

7) Next, we’ll want to slide out the accumulator side of the line out from above the frame rail. Here you’ll notice the globe and small hard line is in the way. There is also a wiring harness above the AHC line that we have to work around. Begin by sliding/shimming the line towards the front of the vehicle. You’ll want to work the shock side of the line as far up in the engine bay as possible. Note the line bracket below the steering shaft. This position allowed me to pop the other side of the line out from above the frame rail.

8) Use a wedge of choice to persuade the accumulator side of the line out from above the frame rail.

9) Next, we’ll want to pop the shock side of the line out from the engine bay. This is going to take working at both ends of the line simultaneously as well as some bending, twisting, and cursing. Pull the accumulator side of the line towards the rear of the vehicle (TB crossmember) while pulling the shock side of the line out from below the vehicle. The shock side of the line will have to be slightly bent to clear the manifold flange, steering shaft and frame.

 

[CrackedManifold]

10) Once the shock side of the line clears the Exhaust flange & frame, you’re going to have to bend and twist the line to clear the bottom of the sway bar and torsion bar. From there, you should be able to snake the line out from the tranny crossmember, towards the rear of the vehicle.

 

[CrackedManifold]

Sorry for the lack of pics for install. Majority of the time was spent on trial & error fitting without removing components.

11) Installation of the new line will follow the reverse order from removal which comes with new challenges. Some slight bending/persuading is needed seat the line where it needs to be and there will be some trial and error as well. First, you’ll want to tape the threaded end of the union fitting to prevent ruining the threads.

12) Begin by snaking the shock side of the line through the tranny crossmember to below the sway bar. Just let this end hang for the time being.

13) Re-position the accumulator end of the line to the rear TB crossmember.

14) Work the shock-end side of the line back into the engine bay, below the steering shaft once more (this is where most of my trial & error/bending has occurred. You’ll have to play with the position with both ends of the lines as you have the exhaust, crossmember, Torsion bar and sway bar in the way.)

15) Once that step has been conquered, feed the accumulator side of the line over the framerail to the accumulator (remember there is a wiring harness there which the line has snaked below it). This may also take some persuasion with a crowbar/piece of wood.

16) Once the line is over the framerail, pull the accumulator end of the line to the accumulator (you’ll have to work at both ends of the line simultaneously to get them into position).

17) Remove the tape from the threaded fitting and install to the accumulator. Since my line became distorted from bending/installing, I had to slightly bend and reposition the fitting line in order to get to thread into the accumulator.

18) Plug the AHC height control valve back in, bolt the line bracket back to frame (may have to bend the line to get the bolt to line up), bolt the the line back to the hydraulic ram/shock.

19) Open the bleeder screw and Jack the hub up until you see a steady stream of fluid. Close the bleeder screw. Install the wheel.

20) Perform the proper bleeding sequence.

21) Crack open a beer. Or Two. Maybe a shot of burbon as well and reflect back on how much of a PITA this job was.

Overall, this was the most tedious side to replace. Despite easy access to the line, you have the front pipe/cat, tranny crossmember in the way. You can probably get away from altering the line by removing either/or. But doable to replace without removing either if you’re comfortable with bending/prying at the line. I wouldn’t suggest cutting the line as you’ll want to know how you removed it for reverse install. Good luck!